The present invention relates to a composite switching network system in which telephone networks and an internet network are integrated to reduce costs of equipment and operations and, more particularly, to an internet telephony system which make it possible to realize a transfer service from at least one communication state of voice and data obtained through an internet network.
In recent years, with advancement of network technology such as an increase in bandwidth of a local area network (LAN) and advancement of personal computer (PC) technology such as an increase in number of functions of a PC and an increase in speed of a CPU applied to a PC, high-speed communication of voice information between PCs on a plurality of LANs can be practical. With the technical advancement, application software in which conventional voice communication by telephones is executed between PCs on an internet network constituted by LANs and wide area networks (WANs) and a hardware system in which the application software is built are rapidly put on the market. This system is called an xe2x80x9cinternet telephonyxe2x80x9d system. In the internet telephony system, Voice over Internet Protocol (VOIP) technique is used to integrate voice communication and data communication. According to the VOIP technique, on protocol of a network layer used in the Internet, i.e., on a network (IP network) having IP, voice is converted into a frame for a short period of time (about 20 ms), and the frame is added with an IP header to be transmitted and received as a packet. The origin of transmission/reception of voice information on a computer network is old. In 1974, an experiment of the transmission/reception is performed on ARPANET which is the forerunner of the Internet (see Danny Cohen, xe2x80x9cRFC741: Specifications for the Network Voice Protocol (NVP),xe2x80x9d IETF, 1976).
In addition, an internet telephony gateway, having a gateway function for performing communication protocol conversion between a telephone network and an internet network, for realizing communication between the telephone network and the internet network is developed. A system (composite switching network system) which uses the internet telephony gateway to perform repeating between switching equipment of conventional telephone networks by the internet network is proposed. This system has been practically used. The system which performs repeating between switching equipment by the internet network is called xe2x80x9cmiddle omission caused by internet telephonyxe2x80x9d.
In general, telephone communication by a system in which middle omission is caused by internet telephony can be operated at a cost lower than that of telephone communication (voice communication) performed by a conventional telephone network. The middle omission system and a service thereof have rapidly spread.
However, in the conventional technique, the technique of a transfer service made by the middle omission system achieved by the internet telephony gateway is not established.
At present, there are only ITU-T recommendation H.450.2 which defines the service in the internet network and the service of conventional telephone networks. In the recommendation H.450.2, a control procedure and signal protocol of a call transfer service (Call Transfer Supplementary Service: SSCT) in a multimedia communication system in a packet mode regulated by recommendation H.323 are regulated.
When the transfer service is realized by using the services of the internet network and the telephone networks, unnecessary use of the internet circuit is inevitable on a switching equipment side, and the quality of voice communication may be degraded by inter-network matching control of transmission rates performed by CODEC set in gateways. The details of the problem will be described later with reference to the accompanying drawings.
It is, therefore, an object of the present invention to provide an internet telephony system which can perform effective path connection in a transfer operation through an internet network, and not only achieves effective use of internet circuits but also can improve the quality of voice communication and processing capability because CODEC control is not performed.
In order to solve the above problem, there is provided an internet telephony system according to an aspect of the present invention comprising a plurality of switching equipment which accommodate a plurality of terminals which can perform at least one of voice communication and data communication, an internet network including a gate keeper, and a plurality of gateways which connect the plurality of switching equipment to the internet network and make it possible to perform communication through the switching equipment and the internet network by communication protocol conversion, wherein, in a call transfer operation in which transition from a communication state between a first terminal accommodated with a first switching equipment of the plurality of switching equipment and a second terminal accommodated with a second switching equipment of the plurality of switching equipment to a communication state between a third terminal accommodated with the second switching equipment and the second terminal is performed, the gate keeper checks whether path replacement for setting the call transfer operation is required or not, and communication between the second terminal and the third terminal after the call transfer operation is provided by a communication path managed by the second switching equipment.
In this internet telephony system, when the path replacement is required, the gate keeper adds information for path replacement to an information element of a message regulated by a specific communication protocol related to the call transfer operation to notify the second switching equipment on a path replacement side of the information through a corresponding gateway. The specific communication protocol related to the call transfer operation is H.450.2.
The gate keeper has a function of checking whether the path replacement is enabled/disabled by an internet protocol address of a notification destination. More specifically, the gate keeper checks whether path replacement is enabled/disabled by checking whether an internet protocol address of the second terminal of a transfer source destination corresponding to the first terminal of a transfer source coincides with an internet protocol address of the third terminal of a transfer destination.
In addition, each of the plurality of terminals is one of a telephone terminal and a computer terminal.
There is provided an internet telephony system according to another aspect of the present invention comprising a plurality of switching equipment which accommodate a plurality of terminals which can perform at least one of voice communication and data communication, an internet network including a gate keeper, and a plurality of gateways which connect the plurality of switching equipment to the internet network, make it possible to perform communication through the switching equipment and the internet network by communication protocol conversion, and accommodate a terminal which can perform at least one of voice communication and data communication, wherein, in a call transfer operation in which transition from a communication state between a first terminal accommodated with a first switching equipment of the plurality of switching equipment and a second terminal accommodated with a second switching equipment of the plurality of switching equipment to a communication state between a third terminal accommodated with a first gateway of the plurality of gateways corresponding to the second switching equipment, and the second terminal is performed, the gate keeper checks whether path replacement for setting the call transfer operation is required or not, and communication between the second terminal and the third terminal after the call transfer operation is provided by a communication path managed by the second switching equipment and a communication path managed by the first gateway.
There is provided an internet telephony system according to still another aspect of the present invention comprising a plurality of switching equipment which accommodate a plurality of terminals which can perform at least one of voice communication and data communication, an internet network including a gate keeper, and a plurality of gateways which connect the plurality of switching equipment to the internet network and make it possible to perform communication through the switching equipment and the internet network by communication protocol conversion, wherein, in a call transfer operation in which transition from a communication state between a first terminal accommodated with a first switching equipment of the plurality of switching equipment and a second terminal accommodated with a second switching equipment of the plurality of switching equipment to a communication state between a third terminal accommodated with a third switching equipment connected to a first gateway of the plurality of gateways, corresponding to the second switching equipment, and the second terminal is performed, the gate keeper checks whether path replacement for setting the call transfer operation is required or not, and communication between the second terminal and the third terminal after the call transfer operation is provided by communication paths respectively managed by the second switching equipment and the third switching equipment and a communication path managed by the first gateway.
In this configuration, the second switching equipment and the third switching equipment are constituted by a plurality of switching equipment which are physically different from each other. The plurality of switching equipment which are physically different from each other can employ such a configuration that the plurality of switching equipment are logically connected to the same first gateway.
There is provided a gate keeper according to an aspect of the present invention comprising means for checking whether path replacement for setting a call transfer operation is required or not, means for adding information for the path replacement to an information element of a message regulated by a specific communication protocol related to the call transfer operation when the path replacement is required, and means for notifying a second switching equipment on a path replacement side of the information through a corresponding gateway, wherein, in the call transfer operation in which transition from a communication state, through an internet network, between a first terminal accommodated with a first switching equipment and a second terminal accommodated with the second switching equipment to a communication state between a third terminal accommodated with the second switching equipment and the second terminal is performed, communication between the second terminal and the third terminal after the call transfer operation is provided by a communication path managed by the second switching equipment.
There is provided a gate keeper according to another aspect of the present invention comprising means for checking whether path replacement for setting a call transfer operation is required or not, means for adding information for the path replacement to an information element of a message regulated by a specific communication protocol related to the call transfer operation when the path replacement is required, and means for notifying a second switching equipment on a path replacement side of the information through a corresponding gateway, wherein, in the call transfer operation in which transition from a communication state, through an internet network, between a first terminal accommodated with a first switching equipment and a second terminal accommodated with the second switching equipment to a communication state between a third terminal accommodated with the gateway corresponding to the second switching equipment, and the second terminal is performed, communication between the second terminal and the third terminal after the call transfer operation is provided by a communication path managed by the second switching equipment and a communication path managed by the gateway.
There is provided a gate keeper according to still another aspect of the present invention comprising means for checking whether path replacement for setting a call transfer operation is required or not, means for adding information for the path replacement to an information element of a message regulated by a specific communication protocol related to the call transfer operation when the path replacement is required, and means for notifying a second switching equipment on a path replacement side of the information through a corresponding gateway, wherein, in the call transfer operation in which transition from a communication state, through an internet network, between a first terminal accommodated with a first switching equipment and a second terminal accommodated with the second switching equipment to a communication state between a third terminal accommodated with a third switching equipment connected to the gateway, corresponding to the second switching equipment, and the second terminal is performed, communication between the second terminal and the third terminal after the call transfer operation is provided by communication paths respectively managed by the second switching equipment and the third switching equipment and a communication path managed by the gateway.
There is provided a gateway according to an aspect of the present invention comprising means for checking whether path replacement for setting a call transfer operation is required or not, means for adding information for the path replacement to an information element of a message regulated by a specific communication protocol related to the call transfer operation when the path replacement is required, and means for notifying a second switching equipment on a path replacement side of the information through self-gateway, wherein, in the call transfer operation in which transition from a communication state, through an internet network, between a first terminal accommodated with a first switching equipment and a second terminal accommodated with the second switching equipment to a communication state between a third terminal accommodated with the second switching equipment and the second terminal is performed, communication between the second terminal and the third terminal after the call transfer operation is provided by a communication path managed by the second switching equipment.
There is provided a gateway according to another aspect of the present invention comprising means for checking whether path replacement for setting a call transfer operation is required or not, means for adding information for the path replacement to an information element of a message regulated by a specific communication protocol related to the call transfer operation when the path replacement is required, and means for notifying a second switching equipment on a path replacement side of the information through self-gateway, wherein, in the call transfer operation in which transition from a communication state, through an internet network, between a first terminal accommodated with a first switching equipment and a second terminal accommodated with the second switching equipment to a communication state between a third terminal accommodated with the self-gateway, corresponding to the second switching equipment, and the second terminal is performed, communication between the second terminal and the third terminal after the call transfer operation is provided by a communication path managed by the second switching equipment and a communication path managed by the self-gateway.
There is provided a gateway according to still another aspect of the present invention comprising means for checking whether path replacement for setting a call transfer operation is required or not, means for adding information for the path replacement to an information element of a message regulated by a specific communication protocol related to the call transfer operation when the path replacement is required, and means for notifying a second switching equipment on a path replacement side of the information through self-gateway, wherein, in the call transfer operation in which transition from a communication state, through an internet network, between a first terminal accommodated with a first switching equipment and a second terminal accommodated with the second switching equipment to a communication state between a third terminal accommodated with a third switching equipment connected to the self-gateway, corresponding to the second switching equipment, and the second terminal is performed, communication between the second terminal and the third terminal after the call transfer operation is provided by communication paths respectively managed by the second switching equipment and the third switching equipment and a communication path managed by the self-gateway.
With the configuration described above, effective path connection can be performed in a transfer operation through the internet network. Not only effective use of internet circuits can be achieved, but also the quality of voice communication and processing capability can be improved because CODEC control is not performed.